Module: Topographic Indices
(c) 2003 by O.Conrad
Menu: Terrain Analysis > Hydrology > Catchment Area
Description
Calculation of slope and catchment area based topographic indices Topograhic Wetness Index (TWI), USLE LS factor, Stream Power Index.

References:

Boehner, J., Selige, T. (2006):
Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation'
In: Boehner, J., McCloy, K.R., Strobl, J.: 'SAGA – Analysis and Modelling Applications', Goettinger Geographische Abhandlungen, Vol.115, p.13-27

Desmot & Govers (1996):
'A GIS Procedure for Automatically Calculating the USLE LS Factor on Topographically Complex Landscape Units'
Journal of Soil and Water Conservation, 51(5):427.433

Kinnell, P.I.A. (2005):
'Alternative Approaches for Determining the USLE-M Slope Length Factor for Grid Cells.'
http://soil.scijournals.org/cgi/content/full/69/3/674

Moore, I.D., Grayson, R.B., Ladson, A.R. (1991):
'Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications'
Hydrological Processes, Vol.5, No.1

Wischmeier, W.H., Smith, D.D. (1978):
'Predicting rainfall erosion losses – A guide to conservation planning'
Agriculture Handbook No. 537: US Department of Agriculture, Washington DC.

Parameters
NameTypeIdentifierDescriptionConstraints
Input
Slope Grid (input)SLOPE
Catchment Area Grid (input)AREA
Transmissivity (*)Grid (optional input)TRANSMISS
Output
Topographic Wetness Index (*)Grid (optional output)WETNESSThe Topographic Wetness Index: ln( Area / tan(Slope) )
Stream Power Index (*)Grid (optional output)STREAMPOW
LS-Factor (*)Grid (optional output)LSFACTOR
Options
Method (LS)ChoiceLS_METHODAvailable Choices:
[0] Moore et al. 1991
[1] Desmot & Govers 1996
[2] Boehner & Selige 2006
Area to Length ConversionChoiceLS_AREADerivation of slope lengths from catchment areas. These are rough approximations! Applies not to Desmot & Govers' method.Available Choices:
[0] 1 / cell size (specific catchment area)
[1] square root (catchment length)
Rill/Interrill ErosivityFloating pointDG_EROSIVITYMinimum: 0.000000
StabilityChoiceDG_STABILITYAvailable Choices:
[0] stable
[1] instable (thawing)
(*) optional